Extend the database tables associated with items to include additional item or custom related data. This would also be applicable to hosts.

Here is an example:

For Host "site001-room211-net-rtr-Cisco3750-A-"
For Item "Interface 1/0/1"

How do I attach meta data to the Item such as :
Interface description
Interface speed
Hardware type
Interface tags/keywords
If the interface configuration matches what is documented
etc.

Reference: http://www.zabbix.com/forum/archive/index.php/t-19601.html

This is especially useful for deployments that have automated methods that can periodically update fields using the API. This can also make searching, filtering, grouping hosts and items much more dynamic.

One field could be HTML that would contain description related data. By making it HTML, this permits user defined structure and much easier integration with external tools.
Other fields could be text fields.
These could be used in filtering in various pages of the Zabbix interface.